If you haven’t had or been vaccinated in opposition to COVID-19 in the previous couple of months, the U.S. Facilities for Illness Management and Prevention (CDC) says it is best to get a new booster shot this fall. The newest pictures, which have been authorized in late August and can be found now, have been designed to focus on presently circulating Omicron variants.

The brand new boosters could be given concurrently a seasonal flu shot, the CDC says. However must you get each jabs directly, or area them out? It’s a easy query with a surprisingly advanced reply.

Although the opinion isn’t universal, many consultants, including White House medical adviser Dr. Anthony Fauci, say it is best to get your COVID-19 booster as quickly as you’re eligible—which is no less than two months after your final vaccine dose or three months after your final SARS-CoV-2 an infection. In a recent podcast interview, Dr. Ashish Jha, the White Home’s COVID-19 response coordinator, beneficial getting boosted by Halloween to make sure you’re protected for the vacations and the standard winter virus season.

“Get it now. Should you’ve been vaccinated or [recently] contaminated, it’s superb to attend slightly longer,” Jha stated. “However don’t wait too lengthy. Don’t wait till you get into late November, December. Do it sooner moderately than later.”

Jha’s prompt booster timing strains up with the CDC’s recommendation on flu pictures, which is to get vaccinated by the tip of October. And he has prompt that folks get each pictures directly. “I actually imagine that is why God gave us two arms—one for the flu shot and the opposite one for the COVID shot,” Jha stated throughout a recent press briefing.

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It’s protected to get each pictures on the identical day. Each vaccines may cause unwanted effects—together with soreness on the injection web site, headache, fever, nausea, fatigue, and muscle aches—so when you could really feel crummy if you happen to double up, there’s no medical cause to keep away from doing so. “If an individual needs to get each on the identical time, they will,” says Dr. Alicia Fry, chief of the epidemiology and prevention department inside the CDC’s influenza division. “If that works for that individual, that may be a very environment friendly use of their time.”

Dr. Richard Zimmerman, who directs the Pittsburgh Vaccination Analysis Group and has served on the CDC’s vaccine advisory committee, agrees that now is an effective time to get a COVID-19 booster, since case counts stay excessive throughout the nation. (Zimmerman acquired his Omicron booster in early September.) However in his opinion, September is slightly early to get a flu shot.

“The perfect is to time vaccines earlier than the season of whichever infectious illness it’s,” he says. “Influenza season usually occurs from December to March, so I’m personally holding off on my flu vaccine till October or November.”

A 2021 study discovered that flu shot efficacy wanes by roughly 10% every month after vaccination—so if somebody will get vaccinated in opposition to the flu in September, they might be susceptible to the virus in the event that they’re uncovered in February or March. One other study, which was revealed in 2019 and seemed particularly at aged adults, discovered that if all seniors who usually get vaccinated in opposition to the flu acquired their pictures beginning in October, as an alternative of August or September, greater than 11,000 circumstances of influenza amongst older adults could possibly be prevented in a typical season. The CDC says it’s okay to get vaccinated in November or later, since influenza can flow into till Might.

There’s one other complicating issue, although. Scientists within the U.S. usually look to Australia, which has its flu season in the course of the U.S.’ spring and summer season, to foretell what’s going to occur in the united statesand Australia had an unusually early flu season this yr. The flu isn’t widely circulating in the U.S. yet, however primarily based on what occurred in Australia, it’s doable that may change quickly. “This yr, I do suppose there’s some rationale to getting the influenza vaccine early within the fall,” says Dr. Brandon Webb, an infectious illness specialist at Utah’s Intermountain Medical Heart.

Clearly, loads of variables go into gaming out the perfect vaccination schedule. For individuals at excessive threat of extreme COVID-19 or influenza, it could be value having a dialog with a well being care supplier to weigh these specifics—however most individuals don’t must stress an excessive amount of about timing, Zimmerman says. Ultimately, the most effective time to get vaccinated is everytime you’ll truly do it. And if getting a flu shot and a COVID-19 booster concurrently is the one approach you’ll get each, a two-shot appointment stands out as the approach to go.

“For some individuals, it’s laborious to get to the physician or a medical facility. For them, the comfort of getting each vaccines on the identical time could outweigh the chance of waning [protection],” Zimmerman says. “Should you don’t get in since you’re making an attempt to time it completely,” you’ll be left with no safety in any respect.

Extra Should-Learn Tales From TIME

Write to Jamie Ducharme at jamie.ducharme@time.com.

Extra Should-Learn Tales From TIME

Write to Jamie Ducharme at jamie.ducharme@time.com.